On 6/10/21 9:11 AM, Marc Nieper-Wißkirchen wrote:
> A typical coding error would be:
>
> (let ((mymap (mapping default-comparator 'a 1 'b 2)))
>    (mapping-set! mymap 'c 3)
>    (mapping-ref mymap 'c)) ;=> 3 ???
>
> In our proposal, a quality implementation will set a flag on the corpse of MYMAP that has been left by mapping-set!. This flag will make sure that an assertion violation is triggered by the subsequent mapping-ref.
>
> Note that SRFI 1 is, again, quite different. Although it began the use of linear update procedures, it works on a concrete, transparent data type. There, I don't have room for an I-am-a-corpse-flag.

Better to catch this at compile-time - which also works for SRFI-1.
However, you'd need a mechanism to annotate procedure with a 'result-must-be-used
property, which the compiler can check.  (Calls using apply would be too
difficult to handle, but would presumably be rare for linear-upadte procedures.)

Even better: Don't. It's a user-hostile idiom, which should be resticted
to "for-expert-users-only" libraries.
--
	--Per Bothner
xxxxxx@bothner.com   http://per.bothner.com/